Page 1 of 73 Diabetes
Glucagon-like peptide-1 receptor agonists increase pancreatic mass by induction of protein synthesis
Jacqueline A. Koehler1, Laurie L. Baggio1, Xiemin Cao1, Tahmid Abdulla1, Jonathan E. Campbell, Thomas Secher2, Jacob Jelsing2, Brett Larsen1, Daniel J. Drucker1
From the1 Department of Medicine, Tanenbaum Lunenfeld Research Institute, Mt. Sinai Hospital and 2Gubra, Hørsholm, Denmark
Running title: GLP 1 increases pancreatic protein synthesis
Key Words: glucagon like peptide 1, glucagon like peptide 1 receptor, incretin, exocrine pancreas
Word Count 4,000 Figures 4 Tables 1
Address correspondence to:
Daniel J. Drucker M.D.
Lunenfeld Tanenbaum Research Institute
Mt. Sinai Hospital 600 University Ave TCP5 1004
Toronto Ontario Canada M5G 1X5
416 361 2661 V 416 361 2669 F [email protected]
1
Diabetes Publish Ahead of Print, published online October 2, 2014 Diabetes Page 2 of 73
Abstract
Glucagon like peptide 1 (GLP 1) controls glucose homeostasis by regulating secretion of insulin
and glucagon through a single GLP 1 receptor (GLP 1R). GLP 1R agonists also increase pancreatic weight in some preclinical studies through poorly understood mechanisms. Here we
demonstrate that the increase in pancreatic weight following activation of GLP 1R signaling in
mice reflects an increase in acinar cell mass, without changes in ductal compartments or β cell
mass. GLP 1R agonists did not increase pancreatic DNA content or the number of Ki67+ cells in
the exocrine compartment, however pancreatic protein content was increased in mice treated
with exendin 4 or liraglutide. The increased pancreatic mass and protein content was
independent of cholecystokinin receptors, associated with a rapid increase in S6 kinase phosphorylation, and mediated through the GLP 1 receptor. Rapamycin abrogated the GLP 1R
dependent increase in pancreatic mass but had no effect on the robust induction of Reg3α and
Reg3β gene expression. Mass spectrometry analysis identified GLP 1R dependent up regulation of proteins important for translation, and export, including cytochrome P450, Fam129a, eIF4a1,
Wars, and Dmbt1. Hence, pharmacological GLP 1R activation induces protein synthesis leading to increased pancreatic mass independent of changes in DNA content or cell proliferation in mice.
2
Page 3 of 73 Diabetes
Gut hormones secreted from specialized endocrine cells subserve multiple functions integrating
control of food ingestion, gut motility, and the digestion, absorption and assimilation of
nutrients. The actions of enteroendocrine peptides to control lipid metabolism, body weight and
glucose homeostasis have engendered considerable translational interest given the increasing
incidence of dyslipidemia, obesity and diabetes. Glucagon like peptide 1 (GLP 1), secreted from
enteroendocrine L cells, reduces food intake, inhibits gastric emptying, and produces weight loss.
GLP 1 also inhibits chylomicron secretion from enterocytes and lowers triglyceride levels in
both preclinical and clinical studies (1). The most extensively studied action of GLP 1 is that of
an incretin hormone, augmenting insulin and inhibiting glucagon secretion following meal
ingestion, through actions targeting endocrine cells in the pancreas. Collectively, the
glucoregulatory actions of incretin hormones led to development of two distinct drug classes that
lower glucose by potentiation of incretin action, dipeptidyl peptidase